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For anyone interested, they started phasing these out in the 60s or early 70s as they were replaced by electronic ones. They were engineering marvels. I couldn't find a picture of this exact model, but here's a similar one. You can see where the handle would have gone in OPs picture.

I once took one of these things apart to clean and lubricate it and put it back together to give as a gift. Holy shit there were so many parts. Buttons, springs, levers everywhere. I took every single piece out and cleaned it. I was sweating bullets putting it back together, but it worked!

Yes, you're right. In all three points. I'm collecting and restoring these wonderful machines (beside slide rules & other mathematical helpers from the past). Sometimes I go into schools and tell the kids about those things.

It's extremely fascinating how many ways people found to solve the problem in a mechanical way, before there were tubes, transistors or chips. And how beautiful and ingenious they were. It's worth preserving them for generations to come. Plus I find it calming to use 'em, don't know why.

Here's a video about how the comptometer works, an adding machine produced from 1887 (!) onwards with a fascinating carry mechanism, quick as one hundreds of a second (in a well maintained machine). Gotta love that.

YSK there's an awesome museum in Bonn, germany, only for the history of calculating machines:
http://www.arithmeum.uni-bonn.de
Definitely worth visiting when you're around that place. Here is one wall in there.

The episode of tested was about the Curta, when I'm not entirely wrong. Thats a special one, very small, very advanced for the time it was invented, and very well build. And very difficult to repair, although there are newly made spare parts around, hail to the 3d printers. The prices are constantly rising for these, that's right. And sad, cause there aren't so few out there.

The same way babbage did - by evolution from a simpler model. Ultimately, you start by building something like a one digit adder, and then expand that to a 10 digit adder, then you think about how multiplication is just successive addition, and so on

Its a funny thing that people find these mechanical calculators amazing, but not so much the CPU in their devices, which is hundreds of times more complicated. I think it boils down to the fact that we can see all of the complex levers and mechanical workings of the calculator whereas we don't really see much of the inner workings of a CPU, so it seems a lot simpler to the naked eye.

Edit: Don't get me wrong, this calculator is ridiculous and awesome. but a CPU can do a million times more than this calculator in shorter time, and i think we kind of take it for granted how amazing it is.

I'm a programmer, so I value the CPU, I promise. I just think it's pretty fascinating that someone figured out how to create a machine, using nothing but motion and force, that can add numbers together. It can do it in the complete absence of electricity. It DID do it in the complete absence of electricity.

It's taking the force of your finger, and literally converting it into math.

It's actually easier to understand once you recognise the basic building block being ratcheted wheels with 10 positions, and that you can add one wheel to another by moving wheel A for every position in wheel B until you hit 0 on wheel B. From there it's just a step of scaling it up to multiple digits, then recognising that A*B is the same as adding A to A, B-1 times. Division is a little harder, but not much.

It's not hard to imagine how a CPU works, it's just that modern CPU's have evolved to be extremely complex mostly because we've perfected manufacturing over decades to make more things fit into the same form factor. In fact you can make your own CPU at home with relatively basic knowledge.

This, on the other hand... I don't know how to even start designing this, other than hundreds of prototype revisions. And to imagine it was well before CAD age, just makes it exponentially worse.